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[求助]求三角形最大角的疑惑,是DS的题

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楼主
发表于 2008-12-31 21:14:00 | 只看该作者

[求助]求三角形最大角的疑惑,是DS的题

In ΔPQR, if PQ = x + 2, and PR = y, which of the three angles of ΔPRQ has the greatest
degree measure?
(1) y = x + 3
(2) x = 2

解释:
In any triangle, the largest angle is opposite the longest side. To determine the longest side it
suffices to determine whether y > x + 2. Since x + 3 > x + 2, it follows from (1) that y > x + 2.
Statement (1) alone is therefore sufficient. From (2) it follows that PQ = 2 and QR = 4. Thus, y can
be any value between 2 and 6; it follows that y > x, but it cannot be concluded that y > x + 2.
Statement (2) alone is therefore not sufficient. Therefore, statement (1) ALONE is sufficient, but
statement (2) alone is not sufficient to answer the question.

题目的答案是A. 可是从STATEMENT (1)中,只可以知道Y>X, 怎么知道Y就是最大边呢?三角形一共有3边,不是还有最后一边未知吗,为什么题目却说STATEMENT 1 是 SUFFICIENT?


[此贴子已经被作者于2008-12-31 21:14:25编辑过]
沙发
 楼主| 发表于 2009-1-1 18:40:00 | 只看该作者

In ΔPQR, if PQ = x + 2, and PR = y, which of the three angles of ΔPRQ has the greatest
degree measure?
(1) y = x + 3
(2) x = 2

解释:
In any triangle, the largest angle is opposite the longest side. To determine the longest side it
suffices to determine whether y > x + 2. Since x + 3 > x + 2, it follows from (1) that y > x + 2.
Statement (1) alone is therefore sufficient. From (2) it follows that PQ = 2 and QR = 4. Thus, y can
be any value between 2 and 6; it follows that y > x, but it cannot be concluded that y > x + 2.
Statement (2) alone is therefore not sufficient. Therefore, statement (1) ALONE is sufficient, but
statement (2) alone is not sufficient to answer the question.

题目的答案是A. 可是从STATEMENT (1)中,只可以知道Y>X, 怎么知道Y就是最大边呢?三角形一共有3边,不是还有最后一边未知吗,为什么题目却说STATEMENT 1 是 SUFFICIENT?

板凳
发表于 2009-1-1 20:46:00 | 只看该作者

lz发了两遍,一直觉得题目有点怪异,因为觉得这道做过,在OG11里,280页32题,你去看看吧,你发的是不是漏了一些信息啊???

地板
 楼主| 发表于 2009-1-7 17:17:00 | 只看该作者
以下是引用zl35在2009-1-1 20:46:00的发言:

lz发了两遍,一直觉得题目有点怪异,因为觉得这道做过,在OG11里,280页32题,你去看看吧,你发的是不是漏了一些信息啊???

我是在网上DOWNLOAD OG10做的,不明白他说的解释,不知道是不是题目有遗漏啊,是在网上下的。晕死了,唉
5#
发表于 2009-1-7 19:05:00 | 只看该作者

题目有漏洞

6#
 楼主| 发表于 2009-1-7 22:26:00 | 只看该作者
以下是引用eagle7772在2009-1-7 19:05:00的发言:

题目有漏洞

有没有人能把原题给我一下,给个连接也行。拜托拜托
7#
发表于 2009-1-7 23:22:00 | 只看该作者
pq=x,qr=x+2,pr=y,别的一样,就少了个条件
8#
 楼主| 发表于 2009-1-8 14:48:00 | 只看该作者
以下是引用eagle7772在2009-1-7 23:22:00的发言:
pq=x,qr=x+2,pr=y,别的一样,就少了个条件

多谢老鹰
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